Walkthrough

In
Goodneighbor behind two locked up warehouses is an alley that leads to a metal door. This is the residence of
Bobbi No-Nose. Speak to her and she will ask you to help with digging some tunnels. You can haggle here for some extra caps if you'd like.

Head to the basement and get rid of the
Mirelurk problem, earning you a promotion. At this point travel to
Diamond City where you will meet back up with Bobbi. She will be in
Diamond City Market. Speak with her where she will explain what the job is really all about and asks you to recruit an individual named
Mel who's jailed by the security of the city.

Enter the office where Mel is being held. You have a few options on how to proceed here:

You may hack the expert terminal to activate the Protectron and free Mel while it engages the guards.

You may sneakily pickpocket a key from the guard or from the desk in the office, and then unlock the cell where Mel is being held.

You may attempt to threaten or persuade the guard to let Mel free.

Once Mel is in tow, return to
Goodneighbor and speak with
Sonya. You will then move through the tunnels, clearing out the areas for fragile sections, digging through and eliminating
Mirelurk enemies here. Continue until you reach the subway tracks where you will encounter some
Feral Ghoul. Keep finding fragile walls and proceed to the strong room. If you get lost at some point you may find your way out by following the glowing red lights.

Locate the metal exit door into the strong room and go into
NH&M Freight Depot. You will encounter
Farenheit where you will discover some more truths about the operation. You can either side with Bobbi and clear the room of opposition and reeive 200 caps as your loot or you may side with Farenheit and eliminate any opposition, and receive from Farenheit the
Ashmaker. It is possible to use a
Charisma check here to persuade Bobbi to walk away peacefully. Whatever you choose affects your alliance with
Goodneighbor so choose carefully.

Not sure why NOBODY on any wiki mentions this, but there is a power armor suit (Mine came with 4 pieces of X-01) behind the "wrong" blast hole in the first room. You have to kill a couple glowing mirelurks for it but I'd say it's well worth it